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. Author manuscript; available in PMC: 2019 Jun 14.
Published in final edited form as: J Med Chem. 2018 May 24;61(11):4946–4960. doi: 10.1021/acs.jmedchem.8b00419

Figure 3.

Figure 3.

Comparison of human CYP17A1 (yellow) and CYP21A2 (cyan), both bound to progesterone (sticks). Orientation of the steroidal core is directed by (1) hydrogen bonding between the C3 oxygen and N202 in helix F for CYP17A1 vs. R234 in helix G of CYP21A2, (2) a shift of the B' helix outward and away from the active site in CYP21A2 compared to CYP17A1, and (3) substitution of I helix G301 in CYP17A1 for Ile291 in CYP21A2. Heme in black sticks with iron as central red sphere. Amino acids are labelled with the CYP17A1 residue given first, followed by the name of the CYP21A2 residue.